The Pittsburgh Symphony Orchestra (PSO) is an American orchestra based in Pittsburgh, Pennsylvania. The orchestra is resident at Heinz Hall, located in Pittsburgh's Cultural District. Since 2008, the orchestra's music director is Manfred Honeck. The orchestra's current president and CEO is Melia Tourangeau.

The orchestra was founded by the Pittsburgh Arts Society with conductor Frederic Archer in 1895, who brought with him a number of musicians from the Boston Symphony Orchestra and led the PSO in its first concert the following year.

In 1898, Victor Herbert was chosen to lead the orchestra. The orchestra traveled at a more frequent rate under Herbert's tenure, performing in Boston, Chicago, Washington, D.C., and Canada. Its personnel included such musicians as Luigi von Kunits (later the first conductor of the Toronto Symphony Orchestra) as concertmaster, first violinist Frederick William Stahlberg, second violinist John Stepan Zamecnik, assistant principal cello Gaston Borch, Paul Henneberg as first flute, and Leon Medaer as first clarinet.

Herbert composed two orchestral works that the Pittsburgh Orchestra premiered: his Suite romantique op. 31 (which he also dedicated to the orchestra) and the tone poem Hero and Leander op. 33. Under Herbert's direction, the Pittsburgh Orchestra played as part of the Pan-American Exposition at the 1901 World's Fair in Buffalo, New York, for which Herbert had also composed an original work for the exhibition titled "Panamericana: Morceau Characteristique" for the Orchestra to perform. His tenure with the Pittsburgh Symphony Orchestra ended in 1904 because of increasingly strident disagreements with the orchestra's manager, George H. Wilson, who disliked Herbert's populist manner and personally despised him.

When Herbert left the orchestra in 1904, the Symphony Society chose as his successor Austrian conductor Emil Paur. Paur took an intellectual approach to his work and avoided theatrics. Trained as a violinist, he had served as conductor of both the Boston Symphony Orchestra and the New York Philharmonic, as well as guest conductor throughout Europe, and held the Pittsburgh Orchestra to the same exacting standards. Paur's programs emphasized the classical repertoire and increased the presence of works by Johannes Brahms, whose music was considered too challenging for most audiences at that time. Additionally, Paur clashed with many of the orchestra's musicians when he prohibited them from accepting outside performing engagements and continued to hire mainly European musicians. Orchestra manager George H. Wilson resigned on December 24, 1906, shortly after the beginning of Paur's third season, saying that his tenure, pride, and pleasure with the orchestra:

Paur remained at the head of the orchestra until it disbanded in 1910.

In the interim, concert promoter May Beegle founded the Pittsburgh Orchestra Association to bring other musical performers to the city.

Antonio Modarelli, an American conductor and composer, became conductor of the Pittsburgh Symphonic Orchestra in 1930. A German newspaper described his conducting as "forceful, authentic, modern music", and he was invited to conduct in Moscow. He had taught at Duquesne University and been a band leader in the Navy prior to his work in Europe and with the Symphony.